Relation between interfacial shear and friction force in 2D materials

Area of Science:

• Materials Science
• Tribology
• Condensed Matter Physics

Background:

• Interfacial properties of atomic layers on substrates are fundamental to electronic, mechanical, and chemical characteristics.
• Controlling phenomena like Fermi level pinning, strain engineering, and superlubricity relies on understanding these interactions.

Purpose of the Study:

• To measure the interfacial transverse shear modulus of atomic layers on substrates.
• To investigate the influence of stacking order, substrate interaction, and intercalated species on this modulus.
• To establish the relationship between interfacial shear modulus and sliding friction in two-dimensional materials.

Main Methods:

• Experimental measurements of interfacial transverse shear modulus on bulk graphite and epitaxial graphene films on SiC.
• Variations in stacking order, twisting, and the presence of intercalated hydrogen were explored.
• Friction force measurements and simulations using simplified friction models.

Main Results:

• The interfacial transverse shear modulus is critically dependent on stacking order and the atomic layer-substrate interaction.
• A reciprocal relationship was demonstrated between friction force per unit contact area and interfacial shear modulus.
• Simulations confirmed that atomic layer-substrate interaction dictates shear stiffness and friction dissipation.

Conclusions:

• The interfacial transverse shear modulus is a pivotal, measurable property for controlling and predicting sliding friction in supported 2D materials.
• Stacking order and atomic layer-substrate interactions are key determinants of interfacial shear modulus.
• Understanding this modulus offers insights into friction mechanisms in layered materials.